Device and method for reducing modulation profile memory size

ABSTRACT

A machine implemented method includes determining a signal modulation for each of a plurality of profiles; generating a first indicator indicating a signal modulation determined for a first profile in the plurality of profiles; generating a second indicator indicating a relationship between the signal modulation for the first profile and the signal modulation for each of the other profiles; notifying at least one node of the first and second indicators.

PRIORITY REFERENCE TO PRIOR APPLICATION

This application claims benefit of and incorporates by reference U.S.patent application Ser. No. 61/377,091, entitled “Throughput Enhancementand Modulation Profile Memory Size Reduction,” filed on Aug. 26, 2010,by inventors Yehuda Azenkot et al.

TECHNICAL FIELD

This invention relates generally to receivers and more particularly, butnot exclusively, provides a method and apparatus for Modulation ProfileMemory Size Reduction in a Multimedia Over Coax Alliance (MoCA) system.

BACKGROUND

The MoCA 2.0 standard defines Modulation Profiles that have a set ofparameters that determines the transmission between nodes, includingpreamble type, cyclic prefix length, modulations per subcarrier andtransmit power. Each MoCA 2.0 Node maintains two PHY profiles for each100 MHz unicast link: one for Nominal Packet Error Rate of 1e-6 (NPER)and one for Very Low Packet Error Rate of 1e-8 (VLPER). Similarly, twoPHY profiles are maintained for 100 MHz Greatest Common Density (GCD) orBroadcast profiles: one for NPER (1e-6) and one for VLPER (1e-8). TheGCD is a modulation format computed by a node for transmission tomultiple recipient nodes. For the GCD or Broadcast format, themodulation used for each subcarrier is chosen to be the greatestpossible modulation density that is less than or equal to the modulationdensity for that subcarrier as reported in the most recent Error VectorMagnitude (EVM) Probe Report the node sent to each of the other nodes.The EVM probe is used to determine the optimum modulation scheme for aset of subcarriers. During a new Node admission procedure, PHY profilesfor both NPER and VLPER are distributed. Since the VLPER packets aremore robust to errors than the NPER packets, the modulations persubcarrier of the VLPER profile are usually equal or lower than thecorresponding modulations per subcarrier of the NPER profile.

However, the above-mentioned modulation schemes require a large amountof memory for each subcarrier. More specifically, 1,920 bits permodulation profile. Assuming 15 nodes, the total memory required forstoring NPER and VLPER modulation profiles is 57,600 bits.

Accordingly, an apparatus and method to reduce modulation profile memorysize may be desirable.

SUMMARY

In an embodiment, a machine implemented method comprises determining asignal modulation for each of a plurality of profiles; generating afirst indicator indicating a signal modulation determined for a firstprofile in the plurality of profiles; generating a second indicatorindicating a relationship between the signal modulation for the firstprofile and the signal modulation for each of the other profiles;notifying at least one node of the first and second indicators.

In an embodiment, A computer-readable medium configured to storeinstructions which enable a controller to perform a method, the methodcomprises determining a signal modulation for each of a plurality ofprofiles; generating a first indicator indicating a signal modulationdetermined for a first profile in the plurality of profiles; generatinga second indicator indicating a relationship between the signalmodulation for the first profile and the signal modulation for each ofthe other profiles; notifying the first and second indicators in thenetwork.

In an embodiment, a method for modulating or demodulating a signalcomprises obtaining a signal modulation for a plurality of profiles,comprising: for a first profile, obtaining a signal modulation for thefirst profile indicated by a first indicator; for any of the otherprofiles, obtaining a signal modulation indicated by a combination ofthe first indicator and at least a part of a second indicator;modulating/demodulating the signal with the obtained signal modulations.

In an embodiment, a device comprises a controller configured to performa method comprising: determining a signal modulation for each of aplurality of profiles; generating a first indicator indicating a signalmodulation at the subcarrier determined for a first profile in theplurality of profiles; generating a second indicator indicating arelationship between the first profile and each of the other profiles; atransmitter configured to notify at least one other device of the firstand second indicators.

In an embodiment, a device comprises a controller, configured to obtain,for a transmission source unit, a signal modulation for a plurality ofprofiles, wherein the obtaining comprises: for a first profile,obtaining a signal modulation for the first profile indicated by a firstindicator; for any of the other profiles, obtaining a signal modulationindicated by a combination of the first and at least a part of a secondindicator; a modulator/demodulator communicatively coupled to thecontroller, configured to modulate/demodulate a signal with the obtainedsignal modulations.

BRIEF DESCRIPTION OF THE DRAWINGS

Non-limiting and non-exhaustive embodiments of the present invention aredescribed with reference to the following figures, wherein likereference numerals refer to like parts throughout the various viewsunless otherwise specified.

FIG. 1 is a block diagram illustrating a transmitter according to anembodiment of the invention;

FIG. 2 is a block diagram illustrating a receiver according to anembodiment of the invention;

FIG. 3 is a block diagram illustrating a modulation per subcarriermemory for NPER and VLPER;

FIG. 4 is a flowchart illustrating a method of reducing representationof NPER modulation per subcarrier;

FIG. 5 is a block diagram illustrating a modulation per subcarriermemory providing a signal modulation (modulation) to a subcarrierbit-mapper or a subcarrier bit-demapper as a function of a profile;

FIG. 6 is a block diagram illustrating a modulation per subcarriermemory for NPER and VLPER unicast profiles using type P5 and P6preambles;

FIG. 7 is a flowchart illustrating a method of reducing therepresentation of modulations of profile that uses Type 6 preamble; and

FIG. 8 is a block diagram illustrating a modulation per subcarriermemory providing a modulation to a subcarrier bit-mapper or a subcarrierbit-demapper as a function of a profile.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

The following description is provided to enable any person havingordinary skill in the art to make and use the invention, and is providedin the context of a particular application and its requirements. Variousmodifications to the embodiments will be readily apparent to thoseskilled in the art, and the principles defined herein may be applied toother embodiments and applications without departing from the spirit andscope of the invention. Thus, the present invention is not intended tobe limited to the embodiments shown, but is to be accorded the widestscope consistent with the principles, features and teachings disclosedherein.

FIG. 1 is a block diagram illustrating a transmitter 100 according to anembodiment of the invention. The transmitter 100 comprises a Low-DensityParity Check (LDPC) error correction encoder 110 coupled to a subcarrierbit-mapper 120, which receives input from a modulation per Subcarriermemory 140. An appender 130 receives input from the bit-mapper 120 and apreamble generator 150. Output of the appender 130 goes to an OrthogonalFrequency Division Multiplexing (OFDM) modulator 160, which outputs to aFilter 170 and then an RF Up-Converter 180.

During operation of the transmitter 100, an input Media Access Control(MAC) frame is first encoded via the Low-Density Parity Check (LDPC)error correction encoder 110. Then, a resulting serial bit stream isassigned to subcarriers according to the modulation profile given in themodulation per subcarrier memory 140 and finally mapping the bitsassigned to each subcarrier to the appropriate Quadrature AmplitudeModulation (QAM) by the mapper 120. The preamble sequence generated bythe preamble generator 150 is appended to the beginning of each packetby the appender 130. The stream of complex numbers input by the appender130 to the OFDM modulator 160 are converted to time domain samples bycomputing an Inverse Fast Fourier Transform (IFFT) on a block of 512complex numbers. Cyclic prefix samples are inserted at the beginning ofeach OFDM symbol. The cyclic prefix samples are generated from the lastNumber of Cyclic Prefix (N_(CP)) samples of the IFFT output which arecopied and prepended to form one OFDM symbol. Then, the stream ofsamples is filtered by the filter 170 and up-converted to theappropriated RF frequency by the RF up-converter 180.

FIG. 2 is a block diagram illustrating a receiver 200 according to anembodiment of the invention. The receiver 200 comprises an RFdown-converter 210 coupled to an analog to digital converter (ADC) 220,which outputs to an OFDM demodulator 230 and a preamble processor 260,which also outputs to the demodulator 230. In an embodiment, the ADC 220comprises two ADCs, one for I and one for Q streams. The demodulator 230outputs to a subcarrier bit-demapper 240, which receives an input from amodulation per subcarrier memory 270. The demapper 240 outputs to anLDPC decoder 250.

During operation of the receiver 200, the down-converter 210 filters anddown-converts a received RF signal to baseband. The signal is convertedto digital samples via two ADCs 220 for the I and Q paths. First thepreamble processor 260 uses the preamble to adjust the signal level,detect the received signal, estimate and correct any carrier frequencyoffset that the received signal may have, and estimate the channel basedat the subcarrier estimation (CE) portion of the preamble. The OFDMdemodulator 230 converts the received samples to frequency domain via aFast Fourier Transform (FFT). The complex samples of each subcarrier areequalized using the equalizer coefficients obtained from the channelestimation based on the CE. Then, the equalized complex samples areconverted to up to 10 values of Log-Likelihood Ratio (LLR) according tothe modulation profile per subcarrier obtained from the modulation persubcarrier memory 270. The LLR values are the soft values needed forLDCP decoding. The LDPC decoder corrects 250 any error that the receivedPHY frame may have and sends the decoded frame to the MAC block.

The modulation used on each subcarrier (i.e., the value of b, asdescribed further below) is specified in the modulation profile in thememory 270, also sometimes called the bit-loading table. This table isset during profiling for each pair of transmitting and receiving nodes.

The modulation profile contains 480 values of b, one for eachsubcarrier: b_(i) is the value at subcarrier i, where it represents thesize of the modulation in bits, running from 1 for Binary Phase SiftKeying (BPSK), 2 for Quadrature Phase Shift Keying (QPSK), 3 for 8-(Quadrature Amplitude Modulation) QAM, through 10 for 1024-QAM. For anysubcarriers for which b_(i)=0, no demapping is needed because no datawere loaded onto the subcarrier. There are 32 subcarriers that alwayscontain zeros. These are called unavailable subcarriers. Any additionalnulls in the modulation profile are called unused subcarriers.

Conventionally, modulation profiles need a large memory to store themodulations per subcarrier. The modulation is determined by 4 bitsrepresenting one modulation out of 10 possible modulations, from BPSK to1024-QAM and a modulation of zero is set for subcarriers that are notused. In MoCA 2.0 there are 480 possible active subcarriers, whichrequire a memory size of 1920 (480*4 bits) bits per modulation profile.Since the MoCA 2.0 receiver needs to support up to 15 nodes, the totalmemory size for storing the modulations of the NPER and VLPER unicastprofiles is 57600 (1920*15*2) bits. Reference will be made in detailbelow to show how to reduce the size of the memory of the modulationsper subcarrier by 37.5% (⅜).

FIG. 3 is a block diagram illustrating a modulation per subcarriermemory for NPER and VLPER. Since the performance of NPER and VLPERprofiles is similar, it's expected that the modulations of thecorresponding subcarriers is the same or different by one bit persubcarrier. Therefore, after the receiver 200 sets the modulationprofile of the VLPER profiles, it can set the modulations of thecorresponding NPER profiles to have the same modulation per subcarrieras the VLPER profile or to be higher by 1 bit per subcarrier. Amodulation higher by 1 bit means that the number of bits per modulationis greater by 1. For example, the higher modulation by 1 bit relative to16-QAM is 32-QAM, where 16-QAM is characterized by 4 bits and 32-QAM ischaracterized by 5 bits. If the VLPER profile has the modulation of1024-QAM, the corresponding modulation of the NPER profile will be also1024-QAM.

The conventional implementation of the modulation per subcarrier memoryrequires 480×4 bits for each of the following profiles: NPER unicastprofile, VLPER unicast profile, NPER GCD profile and VLPER GCD profile.In order to reduce the memory size, the modulation of each subcarrier ofboth pair of NPER and VLPER profiles can be represented by 5 bits only,where 4 bits represent the modulation of each subcarrier of the VLPERprofile and an additional one bit is used to represent whether there isa change in the corresponding modulation of the NPER profile. A bitvalue of 0 means that the subcarrier of the NPER profile uses the samemodulation as the corresponding subcarrier of the VLPER profile, and 1means a higher modulation by 1. The memory size of the pair of NPER andVLPER profiles is 480×5 bits, where it uses 5 bits per subcarrierinstead of 8 bits per subcarrier. Thus, the saving is ⅜=37.5%.

FIG. 4 is a flowchart illustrating a method 400 of reducingrepresentation of NPER modulation per subcarrier. In an embodiment, themethod 400 is performed at a receiver 200 in FIG. 2. Specifically, themethod 400 may be performed by a controller (e.g., a CPU) at thereceiver 200.

In profiling, modulations on each subcarrier for both VLPER and NPERprofiles are determined. As described above, in a conventional method, amodulation is determined by 4 bits representing one modulation out of 10possible modulations. In this embodiment, a first indicator of 4 bits isused to represent a modulation at a subcarrier for a VLPER profile, and1 additional bit, which is an embodiment of a second indicator, is usedto represent a modulation on the same subcarrier for a NPER profile.Therefore, 5 bits are enough for representing the modulations at onesubcarrier for both the VLPER profile and the NPER profile.

In an alternative embodiment, the first indicator of 4 bits are used torepresent a modulation at the subcarrier for the NPER profile, and thesecond indicator of 1 bit is used to represent a modulation at thesubcarrier for the VLPER profile.

In an embodiment, the first indicator is stored at the memory 270 beforethe method 400 starts.

After the receiver 200 finishes with profiling and establishes themodulation per subcarrier for NPER and VLPER profiles, the method 400goes through all subcarriers to determine the second indicator of 1 bitfor the modulation at each subcarrier for the NPER profile.

Specifically, at block 410, the method 400 starts with a subcarrier 0.The method 400 then continues to block 420.

At block 420, the method 400 checks for subcarrier 0 whether themodulation for the NPER profile is the same as the modulation for theVLPER profile. If so, at block 440, a bit of 0 is written in the memory270 to represent a modulation at subcarrier 0 for the NPER profile. Ifthe modulations at subcarrier 0 are different, a bit of 1 is written inthe memory 270 for the NPER profile at subcarrier 0 at block 430, andthe modulation for NPER profile at subcarrier 0 is set to be higher by 1bit relative to the VLPER profile. That is, if the modulation for VLPERprofile is 8-QAM at subcarrier 0, it will be 16-QAM for NPER profile. Inan alternative embodiment, the modulation for the NPER profile may beeven higher relative to the VLPER profile, which is also within thescope of the invention.

Then at block 450, the subcarrier index is incremented and it isdetermined if the subcarrier index is 480 (corresponding to a 481^(st)subcarrier). If so, which means the method 400 has been performed forall subcarriers, the method 400 ends. Otherwise the method 400 returnsto block 420 and is performed for the next subcarrier.

In this embodiment, a first node is going to send signals to a secondnode, the receiver 200 at the second node performs the method 400 andnotifies the first and second indicators generated for each subcarrierto the first node. The received information is then stored in a memory140 in a transmitter 100 at the first node.

FIG. 5 is a block diagram illustrating a modulation per subcarriermemory providing modulations to a subcarrier bit-mapper or a subcarrierbit-demapper as a function of the profile.

When modulating or demodulating, modulations determined and stored mayneed to be retrieved and provided to a subcarrier bit-mapper or asubcarrier bit-mapper. Without loss of generality, the transmitter 100in FIG. 1 is described below in detail.

At the transmitter 100 in FIG. 1, a modulation converter (e.g., acontroller embedded in the modulation per subcarrier memory 140) isconfigured to access the memory 140 and provide modulations to thesubcarrier bit-mapper.

The modulations per subcarrier are scanned for all the 480 subcarriers.Take subcarrier 0 as an example, if the profile is VLPER, the 4 mostsignificant bits (MSBs) obtained from the modulation per subcarriermemory 270 are output without a change. However, if the profile is NPER,the output modulation per subcarrier further depends on a secondindicator (less significant bit, LSB) from the memory 270 stored inassociated with the 4 MSBs. In an embodiment, if the second indicator is0, which means at subcarrier 0, the modulation for the NPER profile isthe same as the modulation for the VLPER profile. If the secondindicator is 1, the 4 MSBs are summed with 1 or other appropriate valueto obtain the modulation at subcarrier 0 for the NPER profile.

FIG. 6 is a block diagram illustrating a modulation per subcarriermemory for NPER and VLPER unicast profiles using type P5 and P6preambles. This embodiment has four unicast high-speed profiles:

1. VLPER Unicast high-speed Profile that uses Type P5 Preamble

2. VLPER Unicast high-speed Profile that uses Type P6 Preamble

3. NPER Unicast high-speed Profile that uses Type P5 Preamble

4. NPER Unicast high-speed Profile that uses Type P6 Preamble

There are two unicast high-speed profiles for VLPER, where one uses TypeP5 preamble and the other one uses Type P6 preamble. Similarly, thereare additional two unicast high-speed profiles for NPER, where one usesType P5 preamble and the other one uses Type P6 preamble. Themodulations per subcarrier of the VLPER profile that uses Type P6preamble is the same or higher by one relative to the correspondingsubcarriers of the VLPER unicast profile that uses Type P5 preamble.Each modulation per subcarrier of the VLPER unicast profile that usesType P5 preamble is represented by 4 bits. Thus, the representation ofthe modulation per subcarrier of the VLPER unicast profile that usesType P6 preamble can use just 1 bit. When the modulation per subcarrieris the same, the one bit that represents the modulation of the VLPERunicast profile that uses Type P6 preamble is set to 0, but when themodulation is higher by 1, it's represented by 1.

Similarly, the modulations per subcarrier of the NPER profile that usesType P5 preamble are the same or higher by 1 relative to the VLPERprofile that uses Type P5 preamble. Therefore, one bit per subcarriercan be used to represent the modulations per subcarrier of the NPERprofile that uses Type P5 preamble. A bit of 0 means that the modulationper subcarrier of the NPER profile that uses Type P5 preamble is thesame as the modulation per subcarrier of the VLPER profile that usesType P5 preamble for the corresponding subcarrier, and bit of 1 meansthat modulation of the NPER profile that uses Type P5 preamble is higherby one relative to the modulation of the VLPER profile that uses Type P5preamble for the corresponding subcarrier.

Similarly, the modulations per subcarrier of the NPER profile that usesType P6 preamble are the same or higher by 1 relative to the NPERprofile that uses Type P5 preamble. Therefore, one bit per subcarriercan be used to represent the modulations per subcarrier of the NPERprofile that uses Type P6 preamble. A bit of 0 means that the modulationof the NPER profile that uses Type P6 preamble is the same as themodulation of the NPER profile that uses Type P5 preamble for thecorresponding subcarrier, and bit of 1 means that modulation persubcarrier of the NPER profile that uses Type P6 preamble is higher by 1relative to the modulation of the NPER profile that uses Type P5preamble for the corresponding subcarrier.

The brute-force implementation of the modulation per subcarrier memorycomprises 4 memory modules, where the size of each one is 480×4 bits.

The memory size can be reduced from 4×480×4 bits to 480×7 bits by using1 bit to represent the modulation per subcarrier for 3 unicast profilesout of the 4 unicast profiles. Therefore, the memory size that storesthe modulations per subcarrier of the four unicast high-speed profilescan be reduced by 56.25% similarly to the memory size reduction of theNPER and VLPER profiles as described above.

FIG. 7 is a flowchart illustrating a method 700 of reducing therepresentation of modulations of profile that uses Type 6 preamble.

Similarly to method 400, the method 700 may be performed by a CPU at thereceiver 200. After the receiver 200 finishes with profiling andestablishes the modulation per subcarrier for NPER profiles that useType P5 and Type P6 preambles and VLPER profiles that use Type P5 andType P6 preambles, the controller starts the method 700.

In an embodiment, before method 700, the modulation per subcarrier ofVLPER profile with a Type P5 preamble is stored in the memoryillustrated in FIG. 6, each represented by 4 bits.

The method 700 starts with subcarrier 0 at block 710.

At block 720, the method 700 checks for subcarrier 0 whether themodulation for VLPER profile with a Type P6 preamble is the same as theVLPER profile with the Type P5 preamble.

If so, the method 700 enters block 740, a bit of 0 is written in thememory for subcarrier 0 for the VLPER profile with the Type P6 preamble.

However, if the modulations at subcarrier 0 are different, at block 730,a bit of 1 is written in association with subcarrier 0 for the VLPERprofile with the Type P6 preamble, and the modulation at subcarrier 0 isset to be higher by 1 bit relative to the VLPER profile with the Type P5preamble.

At block 750, an subcarrier index is incremented and it is determined ifthe subcarrier index is equal to 480, which means the method 700 hasbeen performed for all subcarriers 0-479. If so, the method 700 ends.Otherwise the method 700 returns to block 720 and is performed for thenext subcarrier.

Similarly, for each subcarrier, a modulation for a NPER profile with theType P5 preamble is compared to the modulation for the VLPER profilewith the Type P5 preamble. For each subcarrier, if the modulations arethe same, a bit of 0 is written in the memory for that subcarrier forthe NPER profile with the Type P5 preamble. Otherwise a bit of 1 iswritten in the memory instead, and the modulation at that subcarrier forthe NPER profile with the Type P5 preamble is set to be higher by 1 bitrelative to the modulation at that subcarrier for the VLPER profile withthe Type P5 preamble.

In addition, for each subcarrier, a modulation for a NPER profile withthe Type P6 preamble is compared to the modulation for the NPER profilewith the Type P5 preamble. For each subcarrier, if the modulations arethe same, a bit of 0 is written in the memory for that subcarrier forthe NPER profile with the Type P6 preamble. Otherwise a bit of 1 iswritten in the memory instead, and the modulation at that subcarrier forthe NPER profile with the Type P6 preamble is set to be higher by 1 bitrelative to the modulation at that subcarrier for the NPER profile withthe Type P5 preamble. In an alternative embodiment, the modulation atthat subcarrier for the NPER profile with the Type P6 preamble may becompared to the modulation at that subcarrier for the VLPER profile withthe Type P6 preamble.

Therefore, examining the memory in FIG. 6, for each subcarrier, a secondindicator comprises 3 bits, with the first representing a relationshipbetween a VLPER profile with the Type P5 preamble and a VLPER profilewith the Type P6 preamble, the second representing a relationshipbetween the VLPER profile with the Type P5 preamble and a NPER profilewith the Type P5 preamble and the third representing a relationshipbetween a NPER profile with the Type P6 preamble and the NPER profilewith the Type P5 preamble (or the VLPER profile with the Type P6preamble). In an alternative embodiment of the invention, the bits inthe second indicator may be different from the one illustrated in FIG.6.

FIG. 8 is a block diagram illustrating a modulation per subcarriermemory providing modulations to a subcarrier bit-mapper or a subcarrierbit-demapper as a function of the profile subcarrier bit-mapper andsubcarrier bit-demapper obtaining modulations per subcarrier memory as afunction of the profile. Reference will be made below referring to FIGS.6 and 8.

Similarly to the embodiment in FIG. 6, the modulation converter in FIG.8 may be a controller embedded in the modulation per subcarrier memory(e.g., the memory 270 in FIG. 2).

As shown in FIG. 8, an modulation output by the modulation converter isbased on the profile. If the profile is a VLPER profile with a Type P5preamble, the 4 MSBs obtained from the modulation per subcarrier memoryare output without a change. However, if the profile is a VLPER withType P6 preamble, the output modulation depends on bit number 5 from theleft side of the memory, i.e., the first one in the second indicator. Ifthe bit is 0, the 4 MSB are output without a change, and the modulationfor the VLPER profile with the Type P6 preamble is the same as themodulation for VLPER profile with the Type P5 preamble at the samesubcarrier. If the bit is 1, the 4 MSBs are summed with 1 to obtain themodulation at that subcarrier for the VLPER profile with the Type P6preamble.

Similarly, if the profile is a NPER profile with a Type P5 preamble, themodulation output by the modulation converter depends on bit number 6from the left side of the memory (i.e., the second bit in the secondindicator). If the bit is 0, the 4 MSB are output without a change, andthe modulation of the corresponding subcarrier of the NPER profile withthe Type P5 preamble is the same as the modulation of the VLPER profilewith the Type P5 preamble at that subcarrier. If the bit is 1, the 4MSBs are summed with 1 to obtain the modulation at that subcarrier forthe NPER profile with the Type P5 preamble.

Similarly, if the profile is a NPER profile with a Type P6 preamble, themodulation per subcarrier depends on bit number 7 from the left side ofthe memory (i.e., the third bit in the second indicator). If the bit is0, the modulation for the NPER profile with the Type P6 preamble is thesame as the modulation for the NPER profile with the Type P5 preamble atthat subcarrier. If the bit is 1, the modulation for the NPER profilewith the Type P6 preamble at that subcarrier equals to the modulationfor the NPER profile with the Type P5 preamble plus 1.

This written description uses examples to disclose the invention,including the best mode, and also to enable any person skilled in theart to practice the invention, including making and using any devices orsystems and performing any incorporated methods. The patentable scope ofthe invention is defined by the claims, and may include other examplesthat occur to those skilled in the art. Such other examples are intendedto be within the scope of the claims if they have structural elementsthat do not differ from the literal language of the claims, or if theyinclude equivalent structural elements with insubstantial differencesfrom the literal languages of the claims.

What is claimed is:
 1. A machine implemented method, comprising:determining a signal modulation for each of a plurality of profiles;generating a first indicator indicating a signal modulation determinedfor a first profile in the plurality of profiles; generating a secondindicator indicating a relationship between the signal modulation forthe first profile and the signal modulation for each of the otherprofiles; notifying at least one device of the first and secondindicators.
 2. The method of claim 1, wherein a combination of the firstand second indicators indicates the signal modulation for each of theother profiles.
 3. The method of claim 1, wherein the first profilecomprises a first type profile, the other profiles comprise a secondtype profile, generating the second indicator comprises: comparing thesignal modulation for the second type profile with the signal modulationfor the first type profile; generating the second indicator indicatingif the signal modulation for the second type profile is as same as thesignal modulation for the first type profile.
 4. The method of claim 1,wherein the first profile comprises a first type profile using a firsttype preamble, the other profiles comprise a first type profile using asecond type preamble, generating the second indicator comprises:comparing the signal modulation for the first type profile using asecond type preamble with the signal modulation for the first typeprofile using a first type preamble; generating the second indicatorindicating if the signal modulation for the first type profile using asecond type preamble is as same as the signal modulation for the firsttype profile using a first type preamble.
 5. The method of claim 4,wherein the other profiles further comprise a second type profile usinga first type preamble and a second type profile using a second typepreamble, generating the second indicator comprises: generating a first,second and third sub-indicators, the first sub-indicator indicates ifthe signal modulation for the first type profile using a second typepreamble is as same as the signal modulation for the first type profileusing a first type preamble, the second sub-indicator indicates if thesignal modulation for the second type profile using the a first typepreamble is as same as the signal modulation for the first type profileusing a first type profile, the third sub-indicator indicates if thesignal modulation for the second type profile using a second typepreamble is as same as the signal modulation for the second type profileusing a first type preamble or the signal modulation for the first typeprofile using a second type preamble.
 6. The method of claim 5, whereinthe first indicator is a first binary number, any of the first, secondand third sub-indicators is set to a second binary number if the signalmodulations compared in a corresponding comparison are the same, and isset to a third binary number if the signal modulations compared in thecorresponding comparison are different.
 7. The method of claim 6,wherein the third binary number further indicates that the comparedsignal modulations have a predetermined difference.
 8. The method ofclaim 6, wherein the second binary number is 0 and the third binarynumber is
 1. 9. The method of claim 3, wherein the first type profileincludes a very low packet error rate profile, the second type profileincludes a nominal packet error rate profile.
 10. The method of claim 4,wherein the first type preamble includes a Type P5 preamble, and thesecond type preamble includes a Type P6 preamble.
 11. The method ofclaim 1, wherein the method is performed by a receiver at a device, andwherein the notifying comprises notifying at least one device which isconfigured to perform a modulation and/or demodulation based on thesignal modulations indicated by the first and second indicators.
 12. Themethod of claim 1, wherein the method is performed for each of aplurality of subcarriers.
 13. A computer-readable medium configured tostore instructions which enable a controller to perform a machineimplemented method, the method comprising: determining a signalmodulation for each of a plurality of profiles; generating a firstindicator indicating a signal modulation determined for a first profilein the plurality of profiles; generating a second indicator indicating arelationship between the signal modulation for the first profile and thesignal modulation for each of the other profiles; notifying at least onedevice of the first and second indicators.
 14. The computer-readablemedium of claim 13, wherein the method is performed for each of aplurality of subcarriers.
 15. A method for modulating or demodulating asignal, comprising: obtaining a signal modulation for a plurality ofprofiles, comprising: for a first profile, obtaining a signal modulationfor the first profile indicated by a first indicator; for any of theother profiles, obtaining a signal modulation indicated by a combinationof the first indicator and at least a part of a second indicator;modulating/demodulating the signal with the obtained signal modulations.16. The method of claim 15, wherein the second indicator indicates arelationship between the signal modulation for the first profile and thesignal modulation for each of the other profiles.
 17. The method ofclaim 16, wherein obtaining a signal modulation for any of the otherprofiles comprises: determining if the signal modulation for saidprofile is as same as the signal modulation for the first profile basedon at least a part of the second indicator; if the signal modulationsare the same, obtaining a signal modulation indicated by the firstindicator; and if the signal modulations are different, calculating anupdated indicator based on the first and second indicators and obtaininga signal modulation indicated by the updated indicator.
 18. The methodof claim 15, wherein the method is performed for each of a plurality ofsubcarriers.
 19. A device comprising: a controller, configured to obtaina signal modulation for a plurality of profiles, wherein the obtainingcomprises: for a first profile, obtaining a signal modulation for thefirst profile indicated by a first indicator; for any of the otherprofiles, obtaining a signal modulation indicated by a combination ofthe first and at least a part of a second indicator; amodulator/demodulator communicatively coupled to the controller andconfigured to modulate/demodulate a signal with the obtained signalmodulations.
 20. The device of claim 19, wherein the second indicatorindicates a relationship between the signal modulation for the firstprofile and the signal modulation for each of the other profiles. 21.The device of claim 20, wherein obtaining a signal modulation for any ofthe other profiles comprises: determining if the signal modulation forsaid profile is as same as the signal modulation for the first profilebased on at least a part of the second indicator; if the signalmodulations are the same, obtaining a signal modulation indicated by thefirst indicator; and if the signal modulations are different,calculating an updated indicator based on the first and secondindicators and obtaining a signal modulation indicated by the updatedindicator.
 22. The device of claim 20, wherein the controller and themodulator/demodulator are configured to perform the processes for eachof a plurality of subcarriers.